Low-pressure loose GO composite membrane based on Langmuir-Blodgett assembly for effective dye/salt separation

To overcome the pervasive trade-off between permeability and selectivity in membrane separation, this study developed a loose nanofiltration membrane operable at low pressure by constructing ordered graphene oxide (GO) nanochannels via Langmuir–Blodgett self-assembly. This technique enables precise layer-by-layer deposition of GO monolayers onto a highly porous electrospun polyacrylonitrile nanofibrous substrate, forming an ultrathin selective layer that achieves high-efficiency separation under low operating pressure. By tuning the number of deposited GO layers, the separation performance can be systematically regulated: as the layer count increases, the rejection of dyes such as Congo Red and Methylene Blue rises significantly, reaching 85–90% for the four-layer GO membrane. In salt separation, the membrane attains a Na₂SO₄ rejection of approximately 80%, with the rejection order following Na₂SO₄ > MgSO₄ > NaCl > MgCl₂, which is attributed to the synergistic effect of size sieving and Donnan exclusion. Furthermore, the GO-coated membrane exhibits enhanced antifouling performance, characterized by high flux recovery and low irreversible fouling. This work not only provides a high-performance loose nanofiltration membrane for dye/salt separation, but also offers a scalable strategy for fabricating precisely structured two-dimensional nanochannel membranes, demonstrating promising potential for wastewater treatment and resource recovery.